The embodiments herein relate to a bearing monitoring system for an air cycle machine and methods associated therewith.
Environmental control systems (ECS) are utilized on various types of aircraft for several purposes, such as air supply systems and/or cabin conditioning systems for the aircraft. For example, components of the ECS may be utilized to remove heat from various aircraft lubrication and electrical systems and/or used to condition aircraft cabin air. The cabin air conditioner may be supplied by a conventional bleed air supply or by one or more cabin air compressors (CACs) which compress air entering the system from an outside source or from a ram air system. The compressed air is delivered to an air cycle machine (ACM) to bring it to a desired temperature and then delivered to the aircraft cabin.
The ACM includes a compressor and a turbine each supported on a common shaft which rides upon hydrodynamic bearings in a housing. A pair of hydrodynamic, foil-type journal bearings supports the shaft. The shaft includes a thrust runner. Axial forces imparted on the shaft are counteracted by a pair of thin foil hydrodynamic thrust bearings arranged on either side of the thrust runner. The bearings are important for overall system health due to there being only thousandths of an inch of operating clearance between the shaft and the bearings. Typically, foil bearings are designed to last the life of the ACM with no scheduled maintenance, however, when the bearings do degrade, or fail, the damage to the ACM may be extensive, causing the need for replacement or costly repair. Additionally, a failed ACM results in degraded aircraft performance until the equipment is replaced. Typically, because bearing degradation goes unnoticed due to the above-described ACM design life risk prediction of bearing degradation and failure not available.